Due to the modification in the request limits we have a nice error if we execute the old code:

TweepError([{'message': 'Rate limit exceeded', 'code': 88}],)

With API 1.0 you were able to make a maximum of 150 requests per hour, and with each request it was possible to obtain a list of 100 friends/followers. Now we have a limit of 15 requests per 15 minutes, so with the same code we get a lower amount of users. However, the new API update also added some new request types, like the possibility to get a list of up to 5,000 follower/friend ids per request! So the new implementation of the script takes these ids, compares them with the local file and then makes some bulk requests to get the users' information, but just in the case of new followers, saving requests.

After these modifications we can use the script as before and without errors (if we don't reach the limits, of course). The annoying thing of this is that we have to create a Twitter application and copy the credentials within the script, or use an alternative option, like getting these values from environment variables. You can download the new code from here.